Eduardo Estigoni

MC9S08GT60 + SCI @ fast rate: should I use Internal or Exterrnal clock?

Discussion created by Eduardo Estigoni on Sep 11, 2007
Latest reply on Sep 12, 2007 by Alban Rampon
Hi Guys,

I 've been reading some information in this forum about clock configuration, however I couldn't make a decision yet...

I will be sampling 4 analog signals via 4 ADC pins and sending them via SCI (through an FTDI chip) to an USB port. So that it is very interesting to reach the maximum speed I can.

In order to use a rate of 250000 baud (it is tha maximum USB 2.0 speed, right?) do I need (or is it better) to use an external cristal in the MCU? As far as I understand, the fastest  cristal I can use is 16MHz... Is it right?

If using the internal oscilator, can I reach the same speed I would reach by using the external cristal?  Or, is it fast enough to sample all these data?

Please let me know what is the best option.